This is a newly established laboratory that will focus on the role of Kaposi's sarcoma-associated herpes virus (KSHV) in the pathogenesis of KS. KSHV is a newly described gamma-herpesvirus that is present in lesional tissue of all clinical types of KS. However, it is unknown whether this virus contributes to the development of KS. Initially, the lab will complete projects begun within the past year that concern tissue distribution and sequence variation of KSHV. Using blood and skin samples obtained from U.S. and Tanzanian patients with KS, we are isolating, cloning, and sequencing two KSHV open reading frame regions that encode for structural proteins. The aim of this study is to determine whether there are variations in virus isolated in different regions of the world and in different tissue sites (i.e., blood versus skin within the same patient), and whether these differences associate with particular clinical patterns of KS. In another ongoing project, we have detected Epstein-Barr virus and cytomegalovirus DNA in peripheral blood mononuclear cells of 68 children with AIDS, but have failed to detect KSHV in these samples. This study is important for understanding the epidemiology of KSHV; it suggests that infection occurs in adults, as opposed to children, which is unlike most other herpesviruses. Using KS tissue and chronically infected B cell lymphoma cell lines as a source of virus, we have recently begun in vitro infection experiments with KSHV. Cells derived from skin, including microvascular endothelial cells, keratinocytes, fibroblasts, and dendritic cells, will be tested for their ability to support KSHV replication. In addition, cytokine profiles of these cells will be studied before and after infection. We hypothesize that KSHV infection of endothelial cells dysregulates expression of cytokines, which can ultimately lead to the development of KS. Following these in vitro infection experiments, the next step will be to perform in vivo infection experiments with the aim to create a small animal model for KS which incorporates KSHV. Importantly, we suspect that external factors (e.g., cytokines, HIV) play a prominent role in positively and negatively regulating KSHV transcription and replication. Thus, the establishment of in vitro and in vivo infection systems as planned will be critical in identifying and studying these factors in further detail. These studies should contribute greatly to the basic understanding of the pathophysiology of KS and assist in the design of novel anti-viral and/or immunotherapeutic treatments for patients with KS.